Kidney cancer is a rare disease, accounting for only 3% of cancers diagnosed each year (according to the long-term condition guide on the management of kidney cancer published by the High Authority for Health in 2010). These malignant tumors can easily metastasize in the absence of adequate treatment.

According to the Kidney cancer key points file published by the National Cancer Institute in 2022, approximately 11,090 cases were diagnosed in France in 2011. Those affected are mainly men, with an average age of 65 years (National Cancer Institute). In the majority of cases, kidney cancer sets in and develops in patients without symptoms for several years. The disease is detected incidentally during examinations carried out for other reasons, or at a very advanced stage. The treatment of this cancer is mainly based on surgery, i.e. The removal of the affected kidney.

1. Definition of kidney cancer

The kidney is essential to the functioning of the body and its function is to filter the blood and remove toxins. In patients with kidney cancer, a cell in the kidney multiplies uncontrollably, and malignant tumours begin to form. In about 85% of cases, cancer originates in the kidney parenchyma. In this case, it is called renal cell carcinoma (according to the dossier on kidney cancer published by the Léon Bérard Cancer Centre in 2021). The latter can be of three distinct types (National Cancer Institute):

clear cell carcinoma also called adenocarcinoma, which accounts for 80% of cases;
papillary or tubulo-papillary carcinoma, which accounts for 10 to 15% of cases, and which can be type 1 or 2;
chromophobe carcinoma, which accounts for 5% of cases.

Other kidney cancers are particularly rare and occur in the excretory tract. Another form can be observed in young children: Wilms' tumour, also called nephroblastoma. Note that like all cancers, kidney cancer can be classified according to its progression (stage 1, 2, 3 or 4), and its degree of aggressiveness (grade I, II or III). In France, kidney cancer represents about 3% of cancers and was identified in about 11,090 adults in 2011 (National Cancer Institute). Male patients are twice as numerous as females and are on average 65 years old at the time of diagnosis (National Cancer Institute). Kidney cancer has the particularity of remaining silent for a long time (sometimes several years). In 60% of cases, it is diagnosed at a localised stage and incidentally (according to the long-term disease guide on adult kidney cancer, published by the French National Authority for Health in 2010). If it is not discovered early, it can easily metastasise and reach other organs, such as the lungs (in 75% of cases of migration), bones, liver or brain (Haute Autorité de Santé). On average, patients have a 63% chance of survival at 5 years, and 90% when the cancer is still localised (Haute Autorité de Santé).

2. Symptoms of kidney cancer

Unlike other cancers, kidney cancer usually progresses very slowly. Symptoms come late, and the disease can remain silent for many years. Clinical signs can vary greatly and are not always specific. Common symptoms include (National Cancer Institute)

fatigue ;
blood in the urine (macroscopic haematuria): painless, complete, recurrent and spontaneous;
back pain;
a palpable mass in the abdomen
unjustified weight loss;
unexplained fever;
enlargement of a testicular vein in men;
phlebitis or swelling of the legs (less common).

In some patients, metastases may be identified in other organs: lungs, bones, liver or brain. This can lead to other symptoms, such as coughing, shortness of breath or polycythemia (abnormal increase in the number of red blood cells in the blood).

3. Causes of kidney cancer

Kidney cancer affects twice as many men as women. It is also strongly linked to age: on average, patients are 65 years old at the time of discovery. But beyond gender and age, certain risk factors have been clearly identified by medical research. Three of them are particularly likely to promote kidney cancer (National Cancer Institute, Vidal):

dialysis treatment for more than 3 years: this long-term treatment to compensate for kidney failure is conducive to the appearance of cysts in the kidneys and the development of tubulo-papillary type kidney cancer. However, only 2-3% of people on dialysis will develop kidney cancer in their lifetime;
Overweight and obesity: at a BMI (body mass index) of more than 25 kg/m², individuals are much more likely to develop kidney cancer. It is estimated that for an increase of 5 kg/m², the risk is increased by 24-34%;
Smoking: Smoking significantly increases the risk of developing cancer, particularly kidney cancer. Smokers are 1.5 times more likely to develop this disease.

But other risk factors are suspected. These include high blood pressure and repeated exposure to asbestos, arsenic or cadmium. Finally, in a very limited number of patients, kidney cancer can be explained by a familial predisposition. Some rare genetic diseases, such as von Hippel-Lindau disease (VHL) or tuberous sclerosis of Bourneville, are often the cause of kidney cancer.

4. Kidney cancer: when to seek help?

Most patients with kidney cancer discover their disease by chance during examinations for other reasons. This is because the disease develops particularly slowly, and the first clinical signs do not appear until later. Sometimes the first symptoms are not specific and do not alarm patients. However, after a while, kidney cancer can easily metastasise and spread to other organs. It is therefore important to detect it early. According to the file on the symptoms and diagnosis of kidney cancer published by the Cancer Research Foundation in 2018, certain symptoms require medical consultation and additional tests (National Cancer Institute):

the presence of blood in the urine;
pain in the flanks;
an alteration in general health and/or a general loss of weight;
unexplained fatigue and/or fever;
A palpable mass in the abdomen.

Patients who notice these symptoms should be examined by their doctor. Only he or she can determine their origin and possibly suspect a diagnosis of kidney cancer. Finally, it should be noted that in cases of familial forms, kidney cancer may be discovered during routine screening.

5. Kidney cancer investigations and diagnoses

As with the vast majority of cancers, the cure rate for kidney cancer is highly dependent on early diagnosis. In about 60% of cases, it is discovered incidentally, during an ultrasound or abdominal CT scan (Haute Autorité de Santé), carried out in the context of a completely different health problem. First of all, the doctor will question the patient (study personal history and lifestyle), note his or her symptoms, and assess any risk factors. If kidney cancer is suspected, a CT scan of the abdomen is the first step. The aim of this examination is to detect a possible mass. If a mass is found, its size and extension are analysed, but it cannot always be concluded that the tumour is cancerous. It may also be a benign cyst-like tumour. In order to confirm this, the doctor may carry out several additional tests. These may include (Cancer Research Foundation):

an MRI (magnetic resonance imaging) ;
a biopsy: removal of the tumour, microscopic analysis and anatomopathological examination of the tumour or a metastasis;
a thoracic CT scan;
Brain and/or bone imaging: in case of symptoms that may indicate generalization of cancer.

6. Treatments for kidney cancer

The main treatment for kidney cancer is surgery. If the disease is localised and has not spread to other organs, removal of the kidney (or partial or, more often, total nephrectomy) offers a very good chance of cure. If the tumour is very small (less than 4 cm), or if it is impossible to operate (elderly or too weak, associated diseases), alternatives to surgery may be preferred (Cancer Research Foundation). These may involve radiofrequency treatment, cryoablation, or possibly active surveillance. In the case of metastatic kidney cancer, patients may be referred to immunotherapy (interleukin 2 IL-2 and/or interferon-alpha IFN), or to targeted therapies that specifically target cancer cells. This is the case with antiangiogenic treatments or treatments using mTOR inhibitors (Cancer Research Foundation).

Radiation therapy and conventional cytostatic chemotherapy are generally not effective in treating kidney cancer. The survival rate of treated patients depends mainly on the stage of cancer (Haute Autorité de Santé): 90% for stage 1 cancers, and close to zero for end-stage cancers. But with immunotherapy, patients with stage 4 kidney cancer can survive up to 2.5 times longer than those without.

7. How can kidney cancer be prevented?

To prevent kidney cancer, some non-specific measures can be taken. Stopping smoking, eating a healthy and balanced diet, and taking part in regular sports are all highly recommended. In addition, individuals with high blood pressure should be closely monitored and possibly treated.